Question

a truck is moving with a certain uniform velocity. it is accelerated uniformly by 0.75 m/s^2.after 20 seconds, the velocity becomes 72 km/h. find the initial velocity

Answer 1

Answer:

$\boxed{V_{i} = 5\ m/s}$

Explanation:

Given:

Acceleration = a = 0.75 m/s²

Time = t = ?

Final Velocity = $V_{f}$ = 72 km/hr = 20 m/s

Required:

Initial Velocity = $V_{i}$ = ?

Formula:

a = $\frac{V_{f}-V_{i}}{t}$

Solution:

For  $V_{i}$  the formula becomes:

$V_{i} = V_{f}-at$

$V_{i}$  = 20 - (0.75)(20)

$V_{i}$  = 20 - 15

$V_{i}$  = 5 m/s

In Case: If you want it in km/hr:

$V_{i}$  = 5 * 3.6

$V_{i}$  = 18 km/hr

Answer 2

Answer:

5 m/s

Explanation:

acceleration = 0.75 m/s²

time = 20 s

final velocity = 72 km/h = 20 m/s

initial velocity = ?

Apply formula for initial velocity.

$u=-at+v$

$\sf a=acceleration\\t=time\\v=final \: velocity\\u=initial \: velocity$

Solve for u.

$u=-(0.75)(20)+ 20$

$u=-15+20$

$u= 5$